A known device of this type, disclosed in U.S. Pat. No. 4,685,464, is intended for taking measurements on a finger, and is configured as a clothes line clip. An elastically flexible padding member is attached to each arm of the clip. The clip arms are loaded by means of a prebiased shank spring. The human finger is clamped between the two arms. A recess is provided in the surface of each padding member contacting the finger. The transmitter and the receiver lie in these recesses.
Such a device is costly, and has relatively large dimensions. Additionally, the device is not suitable for extensive engagement with the finger, since it can hinder movements of the finger being tested, and can also be slipped out of place or peeled off if such finger movements occur.